CN1761887B - Method and apparatus for processing navigation data in position determination - Google Patents

Abstract

Methods and apparatuses for the processing of false alarms in position determination. At least one embodiment of the present invention estimates and uses measurement false alarm probabilities in the position determination process. In one embodiment, the estimated measurement false alarm probabilities are combined to determine the reliability of the determined position solution or the reliability of the set of measurements as a collection. In one embodiment, the estimated measurement false alarm probabilities are used in the isolation and elimination of faulty measurements. For example, the traditional geometry based metric for identifying a faulty measurement is further weighted according to the measurement false alarm probabilities in order to determine the faulty measurement.

Description

Method and device for processing navigation data in position determination

Cross References to Related Applications

This application claims priority to US Provisional Application No. 60/447,506, filed February 14, 2003, and US Provisional Application No. 60/493,536, filed August 7, 2003.

technical field

The present invention relates to position determination systems, and more particularly to the handling of false alarms.

Background technique

To perform position location in a wireless cellular network, such as a cellular telephone network, several methods perform triangulation based on the use of timing information between each of a plurality of base stations and, for example, cellular telephones. sent between mobile devices of the same class. A method known as Advanced Forward Link Triangulation (AFLT) or Enhanced Observed Time Difference (EOTD) measures at the mobile device the time of arrival of signals transmitted from each of a plurality of base stations. These times are sent to a Position Determining Entity (PDE), such as a positioning server, which uses these received times to calculate the position of the mobile device. The transmission times at the base stations are coordinated such that at a particular instance of time, the time-of-day associated with the plurality of base stations is within a particular margin of error. Use the precise location of the base station and the time of reception to determine the location of the mobile device.

Figure 1 shows an example of an AFLT system in which the times (TR1, TR2 and TR3) of signals received from cellular base stations 101, 103 and 105 are measured at a mobile cellular telephone 111 . This timing data can then be used to calculate the location of the mobile device. Such calculations may be done at the mobile device, or at the location server if the timing information thus obtained by the mobile device is sent to the location server via a communication link. Typically, the time of reception is communicated to the positioning server 115 by one of the cellular base stations (eg base station 101 or 103 or 105). The positioning server 115 is connected to receive data from the base stations via the mobile switching center 113 . A location server may include a base station almanac (BSA) server that provides base station locations and/or base station coverage. Alternatively, the location server and the BSA server may be separate from each other, and the location server communicates with the base station to obtain the base station almanac for location determination. The mobile switching center 113 provides signals (e.g., voice communications) to and receives signals from the land-line Public Switched Telephone System (PSTS) so that signals can be transmitted to and from mobile phones to Other phones (such as landline phones on PSTS or other mobile phones). In some cases, the location server may also monitor transmissions from multiple base stations to determine the relative timing of these transmissions.

In another method, known as Time Difference of Arrival (TDOA), the time at which a signal is received from a mobile device is measured at multiple base stations (eg, the measurement occurs at base stations 101, 103, and 105). Figure 1 applies to this case if the arrows TR1, TR2 and TR3 are reversed. This timing data can then be communicated to a location server to calculate the location of the mobile device.

A third method of position determination involves the use in mobile devices of receivers such as the US Global Positioning Satellite (GPS) system or other Satellite Positioning Systems (SPS), such as the Russian GLONASS system and the proposed European Galileo system receivers, or combined satellite and pseudolite (pseudolite) receivers. Pseudolites are ground-based transmitters that broadcast a PN code (similar to a GPS signal) modulated on an L-band carrier signal, usually time-synchronized with the SPS. Each transmitter can be assigned a unique PN code so that it can be identified by the remote receiver. Pseudolites are useful in situations where it may not be possible to obtain SPS signals from orbiting satellites, such as in tunnels, mines, buildings or other enclosed areas. The term "satellite" as used herein is intended to include pseudolites or equivalents of pseudolites, and the term "GPS signal" as used herein is intended to include signals similar to GPS signals from pseudolites or equivalents of pseudolites. This approach using SPS signal receivers can be fully autonomous, or it can leverage the cellular network to provide assistance data or share position calculations. For simplicity, we refer to these various methods as "SPS". Examples of these kinds of methods are described in US Pat. For example, U.S. Patent No. 5,945,944 describes a method for obtaining precise time information from a cell phone transmission signal, combined with an SPS signal to determine the receiver's position; U.S. Patent No. 5,874,914 describes a method for Sends the Doppler shifts of visible satellites to the receiver to determine the receiver's position; U.S. Patent No. 5,874,914 describes a method of sending satellite almanac data (or ephemeris data) to the receiver over a communications link ) to help the receiver determine its location; U.S. Patent No. 5,874,914 also describes a method that locks to the precise carrier frequency signal of the cellular phone system to provide a reference signal for SPS signal acquisition at the receiver; U.S. Patent No. .6,208,290 describes a method that uses the approximate location of the receiver to determine an approximate Doppler shift to reduce SPS signal processing time; and U.S. Patent No. 5,812,087 describes a method that compares Different records of incoming satellite data messages are used to determine when one of the records is received at the receiver to determine the receiver's position. In a practical low-cost implementation, the mobile cellular communication receiver and the SPS receiver are integrated into the same housing and may actually share common electronic circuitry.

In yet another variation of the above method, the round trip delay (RTD) of the signal sent from the base station to the mobile device and back is obtained. In a similar but alternative approach, the round-trip delay of a signal sent from a mobile device to a base station and back is found. Divide each of these round-trip delays by 2 to determine an estimate of the one-way delay. The base station's location information plus the one-way delay constrains the mobile's location to a circle on the Earth. Two such measurements from different base stations yield the intersection of two circles, which in turn constrains the location to two points on the earth. A third measurement (which could be angle of arrival or cell sector) will resolve this ambiguity.

The combination of AFLT or TDOA with an SPS system is called a "hybrid" system. For example, U.S. Patent 5,999,124 describes a hybrid system in which the location of a cell-based transceiver is determined from a combination of at least the following time measurements: i) ii) and a time measurement representing the travel time of the SPS signal.

Altitude aiding has been used in various methods for determining the position of a mobile device. Altitude assistance is typically based on pseudo-measurements of altitude. The altitude information for the location of the mobile device constrains the possible locations of the mobile device as the surface of a sphere (or ellipsoid) centered at the center of the earth. This information can be used to reduce the number of independent measurements required to determine the location of the mobile device. For example, US Patent No. 6,061,018 describes a method of determining an estimated altitude from information of a cell object, which may be a cell site with a cell site transmitter in communication with a mobile device.

When a minimum set of measurements is available, a unique solution to the navigation equations can be determined for the position of the mobile station. When more than one additional measurement is available, a "best" solution can be obtained that best fits all available measurements (eg, by a least squares solution procedure that minimizes the remaining vectors of the navigation equations). Because when there are redundant measurements, the residual vector is typically non-zero due to noise or errors in the measurements, an integrity-monitoring algorithm can be used to determine whether all measurements are consistent with each other. For example, conventional Receiver Autonomous Integrity Monitoring (RAIM) algorithms can be used to detect consistency problems in a set of redundant measurements. For example, a RAIM algorithm determines whether the remaining vector size of the navigation equation is below a threshold. If the size of the remaining vector is smaller than the threshold, the measurements are considered to be consistent. If the size of the remaining vector is larger than a threshold, then there is an integrity problem, in which case one of the redundant measurements that appears to cause the greatest inconsistency can be removed to obtain an improved solution.

Contents of the invention

Methods and apparatus for handling false alarms in position determination will be described herein. This section will outline some embodiments of the invention.

At least one embodiment of the invention estimates and uses the measurement false alarm probability in the position determination process. In one embodiment, the estimated false alarm probabilities of measurements are combined to determine the reliability of the determined position solution or the reliability of a set of measurements as a collection. In one embodiment, the estimated measurement false alarm probability is used to isolate and remove erroneous measurements. For example, conventional geometry-based metrics for identifying erroneous measurements are further weighted according to the measurement false alarm probability in order to determine erroneous measurements.

In one aspect of the invention, a method for position determination of a mobile station includes determining a first measurement for position determination of the mobile station (such as a GPS signal or time of arrival of the base station signal, pseudorange); and determining a first reliability index from the signal for the first measurement, wherein the first reliability index represents a measurement false alarm probability level for the first measurement. In one embodiment, the reliability level is determined from the first reliability index to represent the probability that the calculated location solution (eg at the mobile station, remote server) for the mobile station usage measurements is not wrong. In one embodiment, the first measured value and the first reliability index are sent to the remote server for location determination of the mobile station. In one embodiment, one or more signal quality indicators determined from the signal used for the first measurement are sent from the mobile station to the remote server, and the one or more signal quality indicators are used at the remote server to determine A first reliability index is determined. In one embodiment, the second measurement is determined from a position determination signal received at the mobile station; a second reliability index is determined from the position determination signal for the second measurement to represent the a measurement false alarm probability level; calculating a location solution for the mobile station using the first measurement and the second measurement; and combining the first reliability index and the second reliability index to determine the reliability of the location solution. In one embodiment, the first and second reliability indicators are used to remove one of the first and second measurements from the position determination when the measurements are inconsistent. In one embodiment, the first reliability index is determined from at least one of the following values: a) the magnitude of the correlation peak; b) the width of the correlation peak; c) the signal strength; d) the signal-to-noise ratio; e) the signal-to-interference ratio ( signal to interference ratio); f) for determining the correlation peak of the first measurement and one or more candidate peaks; and g) for determining the relationship between the signal of the first measurement and the detected signal relation.

In one aspect of the present invention, a method of position determination for a mobile station includes combining a plurality of measurement false alarm indicators to determine the reliability of a position calculated using the plurality of measurements, wherein the plurality of measurement values are false The alarm indicators represent the prior false alarm probability levels of multiple measured values respectively. In one embodiment, the position of the mobile station is calculated using a plurality of measurements, each of which is a value of more than two levels (e.g., a number within a range, such as between 0 and 1). In one embodiment, is determined from one or more signal quality indicators (e.g., a) correlation peak size; b) correlation peak shape indicator; c) signal strength; d) signal-to-noise ratio; and e) signal-to-interference ratio) One of several false alarm indicators for measurements.

In one aspect of the invention, a method of position determination for a mobile station includes, in response to determining that the plurality of measurements are inconsistent, removing one of the plurality of measurements from the position determination using a plurality of a priori false alarm indicators, wherein A plurality of prior false alarm indicators are determined separately for the plurality of measurement values. In one embodiment, the measurement value to be removed among the plurality of measurement values is determined by comparing a plurality of prior false alarm indicators. In one embodiment, a plurality of inconsistency indicators of the plurality of measurement values are respectively determined from the plurality of measurement values, and the plurality of inconsistency indicators are determined by weighting the plurality of inconsistency indicators according to the plurality of prior false alarm indicators respectively. The measurement to drop from the value. In one embodiment, it is determined whether the level of inconsistency between the plurality of measurements is above a threshold, and a plurality of a priori false alarm indicators are determined from the signals used to determine the plurality of measurements, respectively.

The present invention includes methods and apparatus for performing these methods, including data processing systems for performing these methods, and computer-readable media that, when executed on a data processing system, cause the system to perform these methods.

Other features of the invention will become apparent from the accompanying drawings and from the following detailed description.

Description of drawings

The present invention is illustrated by way of example and is not limited to the figures of the drawings, in which like reference numerals designate similar elements.

Figure 1 shows an example of a prior art cellular network for determining the location of a mobile cellular device.

Figure 2 shows an example of a server that can be used with the present invention.

Figure 3 shows a block diagram representing a mobile station according to one embodiment of the present invention.

Figure 4 shows examples of different probability distributions for false alarm and normal measurements, which can be used in the present invention.

Figure 5 illustrates a method of determining the probability of two measurements being close to each other, which can be used in the present invention.

Figure 6 illustrates a method of determining the probability of a false alarm for two measurements, which can be used in the present invention.

Fig. 7 shows a method for determining the location of a receiver according to one embodiment of the present invention.

Fig. 8 shows a detailed method for determining the location of a mobile station according to an embodiment of the present invention.

Fig. 9 shows another detailed method for determining the location of a mobile station according to an embodiment of the present invention.

Detailed ways

The following description and drawings are illustrative of the invention and should not be construed as limiting the invention. Numerous specific details are described in order to provide a thorough understanding of the present invention. However, in certain instances, well-known or conventional details have not been described in order to avoid obscuring the description of the present invention. A reference to one embodiment in the present disclosure is not necessarily used for the same embodiment, and such a reference means at least one.

At least one embodiment of the invention seeks to estimate and use the measurement false alarm probability in the position determination process.

In determining the position of a mobile station or other device, position calculations typically use multiple geometrically distinct measurements, such as range, pseudorange, round-trip delay, and , Earth's surface) associated with other measurements. It is possible that the obtained measurements are actually false alarms, typically caused by poor signal conditions, such that irrelevant signals are incorrectly identified for position determination.

There are many conditions that have the potential to cause false alarms. For example, when acquiring a GPS signal, a local reference signal with a pseudorandom noise code is correlated with the received GPS signal. The correlation output peaks when the timing of the local reference signal and the GPS signal of the same pseudorandom noise code match. Then, the pseudorange is determined from the reference pseudorandom noise code. When the signal strength is low, it is possible to select noise spikes in the correlation output (eg due to thermal noise) as the measurement, causing false alarms. Typically, correlation peaks above a threshold are selected for pseudorange determination. The threshold is typically designed such that when the peak value is above the threshold, the probability of a false alarm is below a certain level. To reduce the probability of false alarms, a higher threshold can be used. However, a higher threshold reduces the usefulness of the measured value when the signal strength is low, since correlation peaks below the threshold are ignored.

Signal interference can also cause false alarms. For example, local reference signals can be cross-correlated with strong GPS signals of different pseudorandom noise codes. Correlation outputs for signals with different pseudorandom noise codes typically have small correlation peaks. When the cross-correlation GPS signal is strong and the GPS signal to be captured is relatively weak, these cross-correlation peaks may be higher than the threshold, causing false alarms. Similarly, when the GPS signal with the same pseudorandom noise code is very strong, smaller correlation peaks appearing at multiple different timing differences in the autocorrelation may also be above the threshold, causing false alarms. The relationship of the GPS signal used to determine the obtained measurements to other detected GPS signals can be used to estimate the probability of false alarms due to cross-correlation.

Multipath signals can also cause false alarms. Reflections of GPS signals through different paths cause additional delays. In some cases, indirect GPS signals may be stronger than direct GPS signals. Thus, multipath signals can be used for measurement determination when the direct GPS signal is weak. Since the multipath signal arrives later than the direct signal, the correlation peak used to determine the obtained measurements in relation to one or more candidate peaks can be used to estimate the probability of a false alarm. In addition, multipath signals may change the shape of the correlation peak (eg, the width of the correlation). Therefore, measurements of the correlation peak shape can also be used as signal quality indicators when determining the probability of false alarms.

In addition, interference from some other signal source (such as jammers or communication signals) may also cause false alarms. Therefore, according to an embodiment of the present invention, a plurality of signal quality indicators (such as correlation peak size, signal-to-noise ratio, signal-to-interference ratio, signal strength, correlation peak to candidate peak relationship, signal for measurement value and other measured signal relationship, among others) can be used to determine the false alarm probability. In conventional receiver designs, some signal quality metrics have been used to determine thresholds (eg, correlation output thresholds) such that the obtained measured values reaching these thresholds have a false alarm probability less than the target value. In one embodiment of the present invention, different levels of a plurality of threshold values are used to estimate the false alarm probability of each measured value. These a priori false alarm probabilities are estimated without combining different geometrically distinct measurements associated with different reference points (eg different GPS satellites or base stations). These prior false alarm probabilities are based on statistics rather than on agreement between different and dissimilar geometric measurements. In one embodiment of the present invention, different levels of threshold values are used to estimate discrete levels of false alarm probability. In one embodiment, an interpolation scheme is used to determine the false alarm probability (eg, using an empirical formula) based on the measured signal quality indicators. The relationship between the false alarm probability and the signal quality index can be obtained from various methods known in the art, such as by collecting statistical data, numerical simulation, numerical simulation, analytical analysis, and others.

In addition to range information (such as pseudoranges), other types of measurements can also be false alarms. For example, the identifier of a base station may be wrong due to a base station lookup operation. Some base stations have the same identification string. Therefore, there is a possibility of wrongly identifying the base station. Currently, base station lookup uses the probability of being correct in its determination. These probabilities may further be used in embodiments of the present invention.

In conventional systems, the measurements are each required to meet a minimum threshold of reliability such that the probability of false alarms for these measurements is sufficiently small for them to be used in position determination calculations. If the measurement does not meet the reliability threshold, the measurement is discarded as a false alarm (or eg no measurement is taken at all if the correlation peak is below the threshold). Therefore, traditional systems use measurements in position calculations only when they meet strict reliability thresholds.

At least one embodiment of the invention uses a more sophisticated approach to estimating and using various degrees of measurement reliability in navigation solutions. The probability of each measurement being a false alarm (or conversely, measurement reliability) is estimated and used in the position calculation stage to determine the probability that the position itself is false. In one embodiment, the estimate of the false alarm probability is expressed as a value between 0 and 1 for both the measurement and the final position calculation. In one embodiment, the estimation of the measurement false alarm probability is performed at the origin of the measurement (eg SPS receiver) and the estimate is sent to the remote server along with the associated measurement for position determination. The server may further refine these false alarm probability estimates (eg using information available at the server) before using the estimates in position determination.

Typically, false alarm measurements and corresponding non-false alarm measurements have very different probability distributions. If a measured value of a parameter is not a false alarm, the measured value typically has a probability distribution (eg, conforms to a Gaussian distribution) within a small range centered around the true value of the parameter. However, if the measurement is a false alarm, the measurement typically has a probability distribution (eg, a relatively uniform distribution) over a wide range around the true value of the parameter to be measured.

Figure 4 shows examples of different probability distributions for false alarm and normal measurements, which can be used in the present invention. In FIG. 4, curve 401 shows the distribution of measurements (eg, pseudoranges) when the measurements are false alarms. The measured values of this false alarm are distributed over a wide range D ₁ (411). Curve 403 shows the distribution of the measured values when the measured values are not false alarms. The distribution of measured values that are not false alarms is centered in a small range D ₂ (413). One embodiment of the present invention considers the relationship between measurements obtained using a dissimilarity profile of false-alarm measurements and non-false-alarm measurements when determining the probability of a false alarm.

For example, when the threshold for the false alarm probability of a measured value is 0.001, the false alarm probability of 0.01 for the first measured value and 0.02 for the second measured value are significantly worse than the threshold. However, if the first measurement agrees well with the second measurement, the first and second measurements can be combined into one measurement, only if both the first and second measurements are false alarms , the measured value is a false alarm. Therefore, if the first measurement and the second measurement are independent of each other, the false alarm probability for the combined measurement is 0.01 x 0.02 = 0.0002, which is significantly better than the threshold of 0.001. Therefore, when these combined measurements with lower reliability agree with each other, these combined measurements can be used without compromising the reliability of the solution.

Figure 5 illustrates a method of determining the probability of two measurements being close to each other, which can be used in the present invention.

For purposes of illustration, it is assumed that both measurements have the same uniform distribution within the range D (507). When the first measurement is at point _xp (505), the second measurement must be within range 509 if the second measurement is within distance d relative to the first measurement. Thus, from the probability distribution of the first measured value and the second measured value, the probability that the two measured values are within the distance d can be obtained. While FIG. 5 illustrates the case where two measurements have the same uniform distribution, one of ordinary skill in the art will understand from this description that such probabilities can be determined for two measurements that have the same distribution or different distributions.

FIG. 6 illustrates a method of determining the probability of a false alarm for two measurements according to one embodiment of the invention. From the false alarm distribution and the non-false alarm distribution (eg curve 401 and curve 403 in FIG. 4 ), the probability that both measured values are within the distance d can be determined respectively, as shown in FIG. 5 . For example, curve 601 shows the probability of two false alarm measurements being within a given distance d; and curve 603 shows the probability of two non-false alarm measurements being within a given distance d. Thus, for small distances d _T , there is a large difference between the probability of two false alarm measurements being within d _T (point 611 ) and the probability of two non-false alarm measurements being within d _T . Therefore, when two measurements are taken within a small distance, there is a good chance that the two measurements are non-false alarm measurements; It is possible that at least one of these two measurements is a false alarm.

For example, 1) If the first measured value and the second measured value are not false alarms, determine that they are both within [-1, 1], but if the first measured value and the second measured value are false alarms, determine that they are both within [-1000, 1000]; and 2) If both the first and second measurements have a 0.2 probability of being a false alarm, then the two measurements have absolutely no chance of being exactly aligned as the probability of a false alarm Sex is very low. Therefore, it is more likely that these two measurements are not false alarms. However, if both the first measurement and the second measurement have a 0.2 probability of being a false alarm within [-1000, 1000], but the first measurement is determined to be within [-1, 1] and the second measurement is determined to be in In [9, 11], since the two measured values deviate too far, the possibility of both measured values as non-false alarms is very small.

In one embodiment of the invention, from the probability of each measurement being a false alarm, the probability that the measurement is within a distance d if the measurement is a false alarm, and the probability that the measurement is within a distance d if the measurement is a non-false alarm The probability within distance d is used to determine (or estimate) the probability that two measurements are false alarm measurements when the two measurements are determined to be within a given distance d. For example, to denote that two measurements are within distance _d , by F to denote that both measurements are false alarms, and by N to denote that at least one of the two measurements is not a false alarm, the following expressions can be used:

P(F|C _d )/P(N|C _d )＝[P(C|F)P(F)]/[P(C|N)P(N)]

where P(C|F) is the probability that the two measured values are within the distance d when the two measured values are false alarms; P(C|N) is the probability of the two measured values when the two measured values are not false alarms The probability that the value is within the distance d; P(F) and P(N) are respectively the probability that two measured values are false alarms and not all are false alarms; and P(F|C _d ), P(N|C _d ) is the probability that the two measured values are false alarms or not all false alarms when the two measured values are within the distance d. P(F), P(N), P(F|C _d ) and P(N|C _d ). From this description, those of ordinary skill in the art can understand that the false alarm probability of each measured value, the relationship between each measured value and the probability distribution of the measured value as a false alarm or a non-false alarm can be used to calculate the solution as a false alarm the posterior probability of .

In one embodiment of the invention, the threshold for the reliability of the measured values is reduced in order to use less reliable measured values for the position determination. This improves sensitivity without compromising the ultimate reliability of the position solution. For example, when a high measurement reliability threshold is used, it is possible that only three measurements are available, which is not sufficient to determine a position. However, when the threshold is lowered slightly, an additional two or more measurements may become available. Utilize the false alarm probability of these additional measurements and the measurement relationship (e.g. measurements of the proximity of the measurements, such as a position solution obtained using one low-reliability measurement along with the three high-reliability measurements and using another The distance between the low-reliability measurements and another position solution obtained from these three high-reliability measurements) can determine whether the relationship between the measurements improves the posterior probability of false alarms for these measurements to some level without compromising the reliability of the final solution.

In one embodiment of the invention, the a priori measured value false alarm probability determined before the execution of the integrity check is used to identify erroneous measured values. For example, when an integrity problem is detected (eg with traditional RAIM/SMO methods), based on redundant measurements, traditional methods can be used to identify erroneous measurements. The probability of having more redundant measurements increases when a lower measurement false alarm probability threshold is used. In addition, in one embodiment of the invention, the prior false alarm probability of the measured values is also used in the identification of false measured values. In one embodiment of the invention, conventional metrics for determining erroneous measurements (eg, geometry-based metrics) are combined with a priori false alarm probabilities to determine indicators for identifying erroneous measurements. For example, conventional metrics can be weighted with prior false alarm probabilities to determine erroneous measurements. When both geometry-based metrics and prior false alarm probability indicators are in terms of probabilities, these probabilities can be combined (eg, multiplied) to generate indicators such that measurements with the worst indicators are discarded. Alternatively, thresholds can be used to identify erroneous measurements if the traditional metric for one of the measurements performs worse than the threshold; however, when traditional methods fail to identify erroneous measurements (such as when all values are below threshold), the wrong measurement value is identified based on the prior false alarm probability. From this description, one of ordinary skill in the art can conceive of many combinations and variations of various methods to use a priori measurement false alarm probabilities in identifying and removing erroneous measurements.

In one embodiment of the invention, even when integrity problems are not detected (e.g. by traditional RAIM methods), individual measured reliability values, geometric properties and internal consistency can be combined to determine the final solution The probability that the estimated or final solution is a false alarm location report conforms to the Gaussian error. When the false alarm probability of the calculated position is low enough, the calculated position may be reported to the end user. Alternatively, the calculated position may be reported to the end user along with a reliability indicator (eg, regardless of the reliability level of the position solution).

Fig. 7 shows a method for determining the location of a receiver according to one embodiment of the present invention. From the signal received at the receiver, at the receiver, operation 701 determines a measurement (eg, pseudorange, round trip time, identifier of the base station) and a false alarm probability indicator for the measurement. In one embodiment of the invention, each individual measurement has an associated false alarm probability determined based on the received signal (e.g. correlation peak size, correlation peak shape/width, signal strength, signal-to-noise ratio, signal-to-interference ratio, used to determine the relationship of the measured value's correlation peak to other candidate peaks, such as peak ratio, peak separation, and used to determine the relationship of the measured value's GPS signal to other detected GPS signals). In one embodiment of the invention, the false alarm probability indicator shows the reliability of the measured value in one of a predetermined number of levels. In one embodiment, the false alarm probability indicator is a number in the range [0, 1]. In one embodiment of the present invention, based on signal quality indicators (such as the size of the correlation peak, the width of the correlation peak, the signal strength, the signal-to-noise ratio, the signal-to-interference ratio, the relationship with other candidate peaks, and the relationship with other detected GPS signals relationship), using a predetermined formula (such as an empirical formula based on statistical data, or a formula based on numerical/analytical probability analysis), the receiver determines the false alarm probability index. Alternatively, the receiver may send one or more signal quality indicators to a remote server that determines and/or improves the false alarm probability of the measurements based on these signal quality indicators. Operation 703 uses the measurements and the false alarm probability indicator to determine a receiver location. In one embodiment of the invention, the reliability of the measurement-based position solution (or the reliability of the redundant measurements as a set) is determined using a false alarm probability indicator. In another embodiment of the invention, when an integrity problem is detected (eg when there is an inconsistency between the measurements used to determine the position), a false alarm probability indicator is used to select the wrong measurement. In addition, in one embodiment of the present invention, a range over which false alarms are likely to occur is also determined. Different sources of false alarms may have different distributions on different scales, and these distributions may be determined or improved at the remote server. In one embodiment of the invention, the likelihood of certain types of false alarm conditions is identified to better identify false alarm distributions for testing consistency of measurements, determining the probability of low reliability measurements Is the alignment consistent.

Fig. 8 shows a detailed method for determining the location of a mobile station according to an embodiment of the present invention. From signals received at the mobile station, operation 801 determines a first measurement (eg, pseudorange, round trip time, identifier of a base station) and a first false alarm probability indicator for the first measurement at the mobile station. From the signal received at the mobile station, operation 803 at the mobile station determines a second measurement (eg, pseudorange, round trip time, identifier of the base station) and a second false alarm probability indicator for the second measurement. Operation 805 sends the first measurement value and the second measurement value and the first false alarm probability indicator and the second false alarm probability indicator from the mobile station to the remote server. At the remote server, operation 807 determines the location of the mobile station using the first measurement and the second measurement. At the remote server, operation 809 determines whether the location is acceptable using the first false alarm probability indicator and the second false alarm probability indicator. For example, the first false alarm probability index and the second false alarm probability index are combined to determine the reliability of the location solution. If operation 811 determines that the measurements are inconsistent, when redundant measurements are available for autonomous integrity monitoring, operations use the first false alarm probability indicator and the second false alarm probability indicator to remove erroneous measurements. For example, a first false alarm probability indicator and a second false alarm probability indicator are used to determine which of the first measurement and the second measurement is false. For example, when identifying and removing erroneous measurements, the inconsistency indicators of the conventional method for the first measurement and the second measurement are weighted according to the first false alarm probability indicator and the second false alarm probability indicator, respectively.

Fig. 9 shows another detailed method for determining the location of a mobile station according to an embodiment of the present invention. From signals received at the mobile station, at the mobile station, operation 901 determines a number of measurements (eg pseudorange, round trip time, identifier of the base station). From the signal received at the mobile station, at the mobile station, operation 903 determines a first false alarm probability indicator for a first measurement of the plurality of measurements. Operation 905 sends the plurality of measurements and the first false alarm probability indicator from the mobile station to the remote server. From the first false alarm probability indicator, using information available at the remote server, at the remote server, operation 907 determines a second false alarm probability indicator for a first measurement value of the plurality of measurements. For example, the server can maintain statistics on false alarms based on the indicators provided by the receivers, which can be used to improve the probability of false alarms of measurements. Additionally, the server may accumulate and improve these statistics based on information collected during location determination services. From the first measurement and the second measurement, at the remote server, operation 909 determines the location of the mobile station. At the remote server, operation 911 determines a probability that the location is or is not wrong using the second false alarm probability indicator. In addition, when the redundant measurement values are not consistent, the second false alarm probability index can be used to remove wrong measurement values.

Therefore, the method of the present invention can improve reliability. The measurements most likely to be false alarms can be selected more reliably. The solution can be utilized to provide a specific metric to indicate the reliability of the solution based on an a priori false alarm probability indicator. In addition, the method of the present invention can improve sensitivity and usability. A lower threshold can be used for each measurement in order to increase the likelihood of having a minimum number of measurements or more for position determination. This makes GPS and AFLT measurements more usable and leads to accurate solutions more often, since combinations of low reliability measurements can be determined to have a high reliability final solution. Embodiments of the invention include a process of estimating the probability of a false alarm for a given measurement at the mobile device by examining the characteristics of selected signals. These features may include signal strength, correlation peak shape, relationship to other candidate peaks, and relationship to other detected GPS signals.

Figure 2 shows an example of a data processing system that can be used as a server in various embodiments of the invention. For example, as described in US Patent No. 5,841,396, the server (201) may provide assistance data, such as Doppler shift or other satellite assistance data, to a GPS receiver in a mobile station. Additionally or alternatively, the positioning server instead of the mobile station may perform the final position calculation (after receiving pseudoranges or other data from which pseudoranges can be determined) from the mobile station and may then forward this position determination to the base station or to the some other system. A data processing system acting as a location server typically includes communication means 212, such as a modem or a network interface. The location server may be connected to a number of different networks through communication means 212, such as a modem or other network interface. Such a network includes a cellular switching center or centers 225, land based telephone system switches 223, cellular base stations (not shown in FIG. 2), other GPS signal receivers 227, or other processors or location servers 221.

A plurality of cellular base stations are typically arranged to cover a geographical area with radio signals, these different base stations being connected to at least one mobile switching center, as is known in the prior art (see, eg, Figure 1). Thus, multiple base stations may be geographically dispersed but connected together by a mobile switching center. Network 220 may be connected to a network of reference GPS receivers that provide differential GPS information and may also provide GPS ephemeris data for use in calculating the position of the mobile system. The network is connected to processor 203 through a modem or other communication interface. Network 220 may be connected to other computers or network components. Network 220 may also be connected to a computer system operated by an emergency telephone operator, such as a Public Safety Answering Point that responds to 911 telephone calls. Various examples of methods for using a location server have been described in a number of US patents including US Patents 5,841,396, 5,874,914, 5,812,087 and 6,215,442.

Location server 201 , which is a form of data processing system, includes bus 202 connected to microprocessor 203 , ROM 207 , volatile RAM 205 , and non-volatile memory 206 . As shown in the example of FIG. 2 , processor 203 is connected to cache memory 204 . Bus 202 interconnects these various components together. Although FIG. 2 shows the nonvolatile memory as a local device connected directly to the rest of the data processing system, it should be appreciated that the present invention may utilize nonvolatile memory remotely located from the system, such as via a modem or A network interface, such as an Ethernet interface, is connected to the network storage device of the data processing system. The bus 202 may comprise one bus or multiple buses connected to each other by various bridges, controllers and/or adapters known in the art. In many cases, a location server can perform its operations automatically without human assistance. In some designs that require human interaction, I/O controller 209 can communicate with displays, keyboards, and other I/O devices.

It should be noted that while Figure 2 illustrates various components of a data processing system, Figure 2 is not intended to represent any particular architecture or manner in which components are interconnected, as these details are not relevant to the present invention. It should also be appreciated that network computers and other data processing systems having fewer components, or possibly more components, can also be used with the present invention and can act as location servers or PDEs.

In some embodiments, the methods of the present invention may be performed on a computer system that is concurrently used for other functions, such as cellular switching, messaging services, and the like. In these cases, some or all of the hardware of FIG. 2 may be shared for multiple functions.

From the above description, it should be apparent that aspects of the invention, at least in part, can be implemented in software. That is, the techniques may be implemented in a computer system or other data processing system in response to its processor executing sequences of instructions contained in memory, such as ROM 207, volatile RAM 205, nonvolatile memory 206, high-speed Buffer memory 204 or a remote storage device. In various implementations, hardwired circuitry may be used in conjunction with software instructions to implement the invention. Thus, the technology is neither limited to any specific combination of hardware circuitry and software nor to any specific source for the instructions executed by the data processing system. Also, throughout the specification, various functions and operations are described as being performed by or caused by software codes to simplify the description. However, those of ordinary skill in the art will appreciate that such expressions imply execution of code by a processor, such as processor 203, to result in these functions.

The machine-readable medium can be used to store software and data that, when executed by a data processing system, cause the system to perform the various methods of the present invention. Such executable software and data may be stored in various locations including, for example, ROM 207 , volatile RAM 205 , non-volatile memory 206 and/or cache memory 204 as shown in FIG. 2 . Portions of such software and/or data may be stored on any of these storage devices.

Accordingly, a machine-readable medium includes information provided (ie, stored and/or transmitted) in a form accessible by a machine (eg, computer, network device, personal digital assistant, manufacturing tool, any device having a set of one or more processors, etc.) Arbitrary mechanisms for information. For example, machine-readable media include recordable/non-recordable media (such as read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, etc.), and electronic, optical, acoustic or Other forms of propagation signals (such as carrier waves, infrared signals, digital signals, etc.), etc.

Figure 3 shows a block diagram representing a mobile station according to one embodiment of the present invention. The mobile station includes a portable receiver that combines a communications transceiver with a GPS receiver for use in one embodiment of the present invention. Combination mobile unit 310 includes circuitry for performing the functions required to process GPS signals as well as the functions required to process communication signals received over the communication link. A communication link such as communication link 350 is typically a radio frequency communication link to another component such as a base station 352 having a communication antenna 351 .

Portable receiver 310 is a combination GPS receiver and communications receiver and transmitter. Receiver 310 includes a GPS receiver stage including acquisition and tracking circuitry 321 and communication transceiver section 305 . Acquisition and tracking circuitry 321 is connected to GPS antenna 301 , and communication transceiver 305 is connected to communication antenna 311 . GPS signals (eg, signal 370 from satellite 303) are received by GPS antenna 301 and input to acquisition and tracking circuitry 321, which acquires the PN (pseudorandom noise) codes of the various received satellite signals. Data generated by circuitry 321 (eg, relevant indicators) is processed by processor 333 for transmission by transceiver 305 . The communication transceiver 305 includes a transmit/receive switch 331 that forwards communication signals (typically RF signals) from the communication antenna 311 to the transceiver 305 and forwards communication signals from the transceiver 305 to the communication antenna 311. In some systems, the T/R (transmit/receive) switch is replaced with a band-splitting filter or "duplexer". Received communication signals are input to communication receiver 332 and passed to processor 333 for processing. A communication signal to be sent from processor 333 propagates to modulator 334 and frequency converter 335 . Power amplifier 336 increases the gain of the signal to an appropriate level for transmission to base station 352 .

In one embodiment of the invention, the combined receiver determines one or more signal quality indicators (e.g., correlation peak size, correlation peak width, signal strength, signal-to-noise ratio, signal-to-interference ratio, relationship to other candidate peaks, and relationship to other detected GPS signals) for determining a measurement false alarm probability indicator for measurements obtained at the receiver (eg, pseudoranges). In one embodiment, the combined receiver sends a signal quality indicator to the base station for determining the measurement false alarm probability of the measurement. In one embodiment, processor 333 determines a false alarm probability according to an index-based formula and transmits the probability along with the measurement to the base station via communication link 351 . In one embodiment, the GPS acquisition and tracking circuit 321 has an automatic gain control (AGC) system that adjusts the gain flatness, which can be analog or digital, so that there is a known total power at the output of the analog-to-digital converter . From signal gain at input, signal distribution (eg Gaussian distribution) and signal processing (eg by processor 333), the correlation threshold is related to false alarm probability (eg by collecting statistics or by numerical simulation or theoretical analysis). Numerical simulation or theoretical analysis typically depends on the signal processing method employed. For example, in one embodiment, by estimating certain characteristics of the strong signal, creating an interference waveform based on these estimated characteristics, and subtracting the interference waveform from a set of correlated outputs of the weak signal to cancel the interference effect of the strong signal, Reduce spurious signals due to interference from strong received signals when processing weaker received satellite signals. Reference may be made to US Patent 6,236,354 for more details on a mobile station for reducing interference in a mobile station. When additional signal processing operations are used to reduce false alarms (or for other purposes), additional simulation operations or analyzes are performed to correlate signal quality indicators and false alarm indicators.

In one embodiment of the invention, communication transceiver portion 305 is capable of using communication signals (e.g., in communication link 350) to extract timing indicators (e.g., timing frames or system time) or to calibrate a mobile station's local oscillator ( not shown in Figure 3). More details on extracting timing indicators or calibrating local oscillators by mobile stations can be found in US Patents 5,874,914 and 5,945,944.

In one embodiment of the combined GPS/communication system 310 of the receiver, the data generated by the acquisition and tracking circuit 321 is sent to the base station 352 via the communication link 350 . Base station 352 then determines the location of receiver 310 based on the data from the remote receiver, the time at which that data was measured, and ephemeris data received from its own GPS receiver or other source of such data. The location data can then be sent back to the GPS receiver 310 or to other remote locations. More details regarding portable receivers utilizing communication links are disclosed in commonly assigned US Patent No. 5,874,914.

In one embodiment of the invention, the combined GPS receiver includes (or is connected to) a data processing system (eg a personal digital assistant or a portable computer). A data processing system includes a bus connected to a microprocessor and memory (eg ROM, volatile PAM, non-volatile memory). The bus interconnects the various components together and also to the display controller and display device and to peripheral devices such as input/output (I/O) devices as are known in the art. The bus may comprise one bus or more buses connected to each other by various bridges, controllers and/or adapters known in the art. In one embodiment, the data processing system includes a communication port (eg, USB (Universal Serial Bus) port, IEEE-1394 bus port). In one embodiment of the invention, the mobile station sends the measurements and the a priori false alarm probabilities (or signal quality indicators) of these measurements to the data processing system (e.g. via an I/O port) so that the data processing system can determine The location of the receiver and the reliability of the solution to that location.

Although the method and apparatus of the present invention have been described with reference to GPS satellites, it should be appreciated that the above description is equally applicable to positioning systems utilizing pseudolites, or a combination of satellites and pseudolites. Pseudolites are ground-based transmitters whose broadcasts are typically modulated to a PN code on an L-band carrier signal, usually synchronized to GPS time (similar to the GPS signal). Each transmitter can be assigned a unique PN code so that it can be identified by the remote receiver. Pseudolites are useful in situations where GPS signals from orbiting satellites may not be available, such as in tunnels, mines, buildings or other enclosed areas. The term "satellite" as used herein is intended to include pseudolites or equivalents of pseudolites, and the term "GPS signal" as used herein is intended to include signals similar to GPS signals from pseudolites or equivalents of pseudolites.

In the previous discussion, the invention has been described with reference to its application on the US Global Positioning Satellite (GPS) system. However, it is clear that these methods are equally applicable to similar satellite positioning systems, and in particular the Russian GLONASS system and the proposed European Galileo system. The GLONASS system differs primarily from the GPS system by utilizing slightly different carrier frequencies rather than using different pseudo-random codes to distinguish transmissions from different satellites. In this case, basically all the circuits and algorithms described above apply. The term "GPS" as used herein includes such alternative satellite positioning systems, including the Russian GLONASS system.

Although the operations in the examples above are described in a particular order, from this description it should be appreciated that various orders and modifications of operations can be employed without being limited to the examples described above.

The above examples are illustrated without presenting some details known in the art, which can be referred to in various publications, such as U.S. Patent Nos. All of these patents are hereby incorporated by reference as noted in the discussion above.

In the foregoing specification, the invention has been described with reference to specific exemplary embodiments. It will be evident that various modifications may be made without departing from the broader spirit and scope of the invention as set forth in the following claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

Claims (58)

1. A location determination method for a mobile station, the method comprising: determining a first measurement for position determination of the mobile station from a position determination signal received at the mobile station; and A probability of a false alarm for the first measured value is estimated from the position determination signal to determine a first reliability index for the first measured value, the first reliability index for identifying erroneous measured values. 2. The method of claim 1, further comprising: A reliability level is determined from the first reliability index to represent the probability that the calculated position of the mobile station using the first measurement is not wrong. 3. The method of claim 2, wherein the position is calculated at the mobile station. 4. The method of claim 1, further comprising: Sending the first measured value and the first reliability index to a remote server for location determination of the mobile station. 5. The method of claim 1, further comprising: sending one or more signal quality indicators from the mobile station to a remote server, the one or more signal quality indicators determined from the position determination signal for the first measurement; Wherein the first reliability indicator is determined using the one or more signal quality indicators at the remote server. 6. The method of claim 1, further comprising: determining a second measurement for position determination of the mobile station from a position determination signal received at the mobile station; and A probability of a false alarm for the second measured value is estimated from the position determination signal to determine a second reliability index for the second measured value, the second reliability index for identifying erroneous measured values. 7. The method of claim 6, further comprising: computing a position solution for the mobile station using the first measurement and the second measurement; and The first reliability index and the second reliability index are combined to determine the reliability of the position solution. 8. The method of claim 6, further comprising: One of the first measured value and the second measured value is removed from a position determination using the first reliability index and the second reliability index. 9. The method of claim 1, wherein the first reliability index is determined from at least one of the following values: a) the size of the correlation peak; b) Correlation peak width; c) signal strength; d) signal-to-noise ratio; e) Signal-to-interference ratio; f) for determining the correlation peak of said first measurement in relation to one or more candidate peaks; and g) The signal used to determine said first measurement is related to other detected GPS signals. 10. The method of claim 1, wherein the first measurement comprises one of the following: a) the arrival time of the signal; and b) Pseudorange. 11. A method of location determination for a mobile station, the method comprising: A plurality of measurement false alarm indicators are combined to determine the reliability of the position calculated using the plurality of measurement values, the plurality of measurement value false alarm indicators respectively representing a priori false alarm probability levels of the plurality of measurement values. 12. The method of claim 11, further comprising: The location of the mobile station is calculated using the plurality of measurements. 13. The method of claim 11, wherein each of the plurality of measurement false alarm indicators is a value of more than two levels. 14. The method of claim 13, wherein each of the plurality of measurement false alarm indicators is a value within a range. 15. The method of claim 11, further comprising: determining one of the plurality of measurement false alarm indicators from one or more signal quality indicators; Wherein the one or more signal quality indicators include one of the following: a) the size of the correlation peak; b) relevant peak shape indicators; c) signal strength; d) signal-to-noise ratio; and e) Signal-to-interference ratio. 16. A method of location determination for a mobile station, the method comprising: In response to determining that the plurality of measurements are inconsistent, removing one of the plurality of measurements from the location determination using a plurality of a priori false alarm indicators individually for the plurality of measurements determined separately. 17. The method of claim 16, wherein the removed one of the plurality of measurements is determined by comparing the plurality of a priori false alarm indicators. 18. The method of claim 16, further comprising: determining a plurality of inconsistency indicators for the plurality of measurements, respectively, from the plurality of measurements; The removed one of the multiple measurement values is determined by weighting the multiple inconsistency indicators according to the multiple prior false alarm indicators respectively. 19. The method of claim 16, further comprising: It is determined whether a level of inconsistency between the plurality of measurements is above a threshold. 20. The method of claim 16, wherein the plurality of a priori false alarm indicators are respectively determined from signals used to determine the plurality of measurements. 21. A data processing system for position determination of a mobile station, the data processing system comprising: means for determining a first measurement for position determination of the mobile station from a position determination signal received at the mobile station; and Means for estimating from said position determination signal a probability of said first measurement being a false alarm for determining a first reliability indicator for said first measurement, said first reliability indicator being used to identify erroneous measurements . 22. The data processing system of claim 21 , further comprising: means for determining a reliability level from said first reliability index representing the probability that the calculated position of the mobile station using said measurements is not wrong. 23. The data processing system of claim 22, wherein the position is calculated at the mobile station. 24. The data processing system of claim 21 , further comprising: means for sending said first measured value and said first reliability index to a remote server for location determination of said mobile station. 25. The data processing system of claim 21 , further comprising: means for transmitting one or more signal quality indicators from said mobile station to a remote server, said one or more signal quality indicators determined from a position determination signal for said first measurement; Wherein the first reliability indicator is determined at the remote server using the one or more signal quality indicators. 26. The data processing system of claim 21 , further comprising: means for determining a second measurement for position determination of the mobile station from a position determination signal received at the mobile station; and means for estimating from said position determination signal a probability of said second measurement being a false alarm for determining a second reliability indicator for said second measurement, said second reliability indicator being used to identify erroneous measurements . 27. The data processing system of claim 26, further comprising: means for computing a position solution for the mobile station using the first measurement and the second measurement; and means for combining said first reliability index and said second reliability index to determine the reliability of said position solution. 28. The data processing system of claim 26, further comprising: Means for removing one of the first measurement value and the second measurement value from a position determination using the first reliability index and the second reliability index. 29. The data processing system of claim 21 , wherein the first reliability index is determined from at least one of the following values: a) the size of the correlation peak; b) Correlation peak width; c) signal strength; d) signal-to-noise ratio; e) Signal-to-interference ratio; f) for determining the correlation peak of said first measurement in relation to one or more candidate peaks; and g) The signal used to determine said first measurement is related to other detected GPS signals. 30. The data processing system of claim 21 , wherein the first measurement comprises one of: a) the arrival time of the signal; and b) Pseudorange. 31. A data processing system for position determination of a mobile station, the data processing system comprising: means for combining a plurality of measurement false alarm indicators, each representing a priori false alarms for said plurality of measurements, to determine the reliability of a position calculated using the plurality of measurements probability level. 32. The data processing system of claim 31 , further comprising: means for calculating the position of the mobile station using the plurality of measurements. 33. The data processing system of claim 31, wherein each of the plurality of measurement false alarm indicators is a value of more than two levels. 34. The data processing system of claim 33, wherein each of the plurality of measurement false alarm indicators is a value within a range. 35. The data processing system of claim 31 , further comprising: means for determining one of said plurality of measurement false alarm indicators from one or more signal quality indicators; Wherein the one or more signal quality indicators include one of the following: a) the size of the correlation peak; b) relevant peak shape indicators; c) signal strength; d) signal-to-noise ratio; and e) Signal-to-interference ratio. 36. A data processing system for position determination of a mobile station, the data processing system comprising: means for, in response to determining that the plurality of measurements are inconsistent, removing one of the plurality of measurements from a position determination using a plurality of a priori false alarm indicators individually for the Multiple measurements are determined separately. 37. The data processing system of claim 36, wherein said removed one of said plurality of measurements is determined by comparing said plurality of a priori false alarm indicators. 38. The data processing system of claim 36, further comprising: means for determining a plurality of indicators of inconsistency for said plurality of measurements from said plurality of measurements, respectively; Wherein the removed one of the multiple measurement values is determined by weighting the multiple inconsistency indicators according to the multiple prior false alarm indicators respectively. 39. The data processing system of claim 36, further comprising: means for determining whether a level of inconsistency between the plurality of measurements is above a threshold. 40. The data processing system of claim 36, wherein the plurality of a priori false alarm indicators are respectively determined from signals used to determine the plurality of measurements. 41. A mobile station of a position determination system, the mobile station comprising: a signal receiving circuit for receiving a position determination signal; a processor connected to said signal receiving circuit, said processor determining a first measurement for position determination of said mobile station from said position determination signal received at said mobile station, said processor A probability of a false alarm for the first measurement is estimated from the position determination signal to determine a first reliability index for identifying erroneous measurements. 42. The mobile station of claim 41 , wherein the processor further determines a reliability level from the first reliability index to represent that the calculated mobile station position using the first measurement is not erroneous probability. 43. The mobile station of claim 41 , further comprising: A communications section connected to the processor, the communications section sending the first measurement and the first reliability indicator to a remote server for use in location determination of the mobile station. 44. The mobile station of claim 41 , wherein the processor further determines a second measurement for position determination of the mobile station from a position determination signal received at the mobile station, and from the The position determination signal estimates a probability of a false alarm for the second measurement to determine a second reliability indicator; wherein the second reliability indicator is used to identify erroneous measurements. 45. The mobile station of claim 44, wherein the processor further calculates a position solution for the mobile station using the first measurement and the second measurement, and combines the first reliability index and the second reliability index to determine the reliability of the location solution. 46. The mobile station of claim 44, wherein the processor further uses the first reliability index and the second reliability index to remove the first measurement and the second reliability index from a position determination. One of the measured values. 47. The mobile station of claim 41 , wherein the first reliability indicator is determined from at least one of the following values: a) the size of the correlation peak; b) Correlation peak width; c) signal strength; d) signal-to-noise ratio; e) Signal-to-interference ratio; f) for determining the correlation peak of said first measurement in relation to one or more candidate peaks; and g) The signal used to determine said first measurement is related to other detected GPS signals. 48. The mobile station of claim 41 , wherein the first measurement comprises one of: a) the arrival time of the signal; and b) Pseudorange. 49. A data processing system for position determination of a mobile station, the data processing system comprising: A memory for storing a plurality of measurement value false alarm indicators and a plurality of measurement values, and the plurality of measurement value false alarm indicators respectively represent prior false alarm probability levels of the plurality of measurement values; and a processor coupled to the memory, the processor combining the plurality of measurements of false alarm indicators to determine the reliability of the position calculated using the plurality of measurements. 50. The data processing system of claim 49, wherein the processor further calculates a position of the mobile station using the plurality of measurements. 51. The data processing system of claim 49, wherein each of the plurality of measurement false alarm indicators is a value of more than two levels. 52. The data processing system of claim 51, wherein each of the plurality of measurement false alarm indicators is a value within a range. 53. The data processing system of claim 49, wherein said processor further determines one of said plurality of measurement false alarm indicators from one or more signal quality indicators; wherein said one or more signal quality indicators Include one of the following: a) the size of the correlation peak; b) relevant peak shape indicators; c) signal strength; d) signal-to-noise ratio; and e) Signal-to-interference ratio. 54. A data processing system for position determination of a mobile station, the data processing system comprising: a memory for storing a plurality of measured values and a plurality of a priori false alarm indicators, the plurality of a priori false alarm indicators are determined separately for the plurality of measured values; A processor coupled to the memory, the processor removing one of the plurality of measurements from a location determination using the plurality of a priori false alarm indicators in response to determining that the plurality of measurements are inconsistent. 55. The data processing system of claim 54, wherein said removed one of said plurality of measurements is determined by comparing said plurality of a priori false alarm indicators. 56. The data processing system of claim 54 , wherein said processor further determines a plurality of inconsistency indicators for said plurality of measurements from said plurality of measurements, respectively; wherein said plurality of a priori The false alarm indicator determines the removed one of the multiple measurement values by weighting the multiple inconsistency indicators. 57. The data processing system of claim 54, wherein the processor further determines whether a level of inconsistency between the plurality of measurements is above a threshold. 58. The data processing system of claim 54, wherein the plurality of a priori false alarm indicators are respectively determined from signals used to determine the plurality of measurements.

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